1. Technical Field
The present invention relates to ignition systems and more specifically to a high data rate simulation technique for use in firing ignition system spark plugs in proper sequence.
2. Discussion
Modern computer controlled spark advance units control ignition timing based on timing information provided by crankshaft or flywheel position sensors. The spark advance unit uses preceding crankshaft position information to fire an ignition coil. In other words, the spark advance unit extrapolates future crankshaft position from past crankshaft position information.
Under this extrapolation method, ignition timing accuracy during transient or dynamic conditions is directly related to the data rate of the crankshaft position sensor. In a low data rate system spark advance timing is extrapolated over a broader timing interval. If the engine speed changes significantly between one reference interval and the next, inaccurate spark advance is possible. In a high data rate system, spark advance timing is extrapolated over a narrow timing interval using more recently updated timing information. If the engine speed changes significantly between one reference interval and the next, accurate spark advance is still provided.
Unfortunately, a high data rate system requires special hardware, usually in the form of a custom-built integrated circuit, which increases the cost of the system. Additionally, the high data rate system places a significant burden on the spark advance control computer which must process the higher data rate signal while performing other tasks.